NO. 6 ANNELIDA, ONYCHOPHORA, AND ARTHROPODA SNODGRASS 3 1 



its new powers of locomotion come into effective service, for now 

 many modern species that habitually live at the bottom rise to the 

 surface in swarms of energetically swimming individuals, both males 

 and females, and here discharge the matured gametes. 



That the genital segments may be of no special physiological 

 importance to the worm, except for carrying, maturing, and distrib- 



Tl Prst 



Fig. 13. — Examples of annelid types. 



A, B, Dinophilns, a very simple archiannelid, perhaps a primitive form, lack- 

 ing teloblastic somites, tentacles, cirri, chaetae, parapodia, and coelomic sacs ; 

 with five pairs of protonephridia, reproductive organs in posterior part of body 

 (A, D. gyrociUatus Schmidt, adult female; B, adult male, from Shearer, 1912). 

 C, Nerilla, an archiannelid with polychaete characters, perhaps a degenerate 

 form, having a coelom, open metanephridia, and direct development (fig. 12 C) 

 (A^. antcnnata Schmidt, from Goodrich, 1912). D, Lopadorhynchns, an errant 

 polychaete (Phyllodocidae), having typical trochophoral development (fig. 8) 

 with metamorphosis (fig. 12 D) producing long series of teloblastic somites 

 (L. uncinatus Fauvel). 



An, anus; AnCir, anal cirrus; Ch, chaetae; Cir, cirrus; /, //, first two 

 somites ; Mth, mouth ; Nph, nephridium ; Ov, ovary ; Papd, parapodium ; Phy, 

 pharynx ; Pip, palpus ; Prst, prostomium ; SlGld, salivary gland ; Tl, tentacles. 



uting the reproductive elements, is shown by the various ways in 

 which the annelids can dispose of these segments without otherwise 

 impairing their functional integrity. There is the well-known case 

 of the palolo worms, Eunice fucata and E. vlridis, for example, 

 which live in crevices of rocks at the bottom of the water, and at the 

 time for spawning detach the rear parts of their bodies, already 



